U.S. patent application number 12/137251 was filed with the patent office on 2009-04-16 for mobile tv system architecture for mobile terminals.
This patent application is currently assigned to Analog Devices, Inc.. Invention is credited to Kamran Sharifi.
Application Number | 20090100475 12/137251 |
Document ID | / |
Family ID | 40535485 |
Filed Date | 2009-04-16 |
United States Patent
Application |
20090100475 |
Kind Code |
A1 |
Sharifi; Kamran |
April 16, 2009 |
MOBILE TV SYSTEM ARCHITECTURE FOR MOBILE TERMINALS
Abstract
A mobile TV system architecture for a mobile terminal that
reduces the processing required by the main processor during
reception of digital broadcasts such as DVB-H. The mobile terminal
architecture includes a main processor system and a mobile TV
receiver device. The mobile TV receiver device includes units for
SI/PSI processing, IP processing and decryption engine. The SI/PSI
(service information/program specific information) processing unit
receives non-protected transport stream (TS) packets and extracts
SI/PSI tables which can be stored in memory local to the receiver
device. The IP processing unit receives decrypted error-corrected
protected packets containing multimedia content. The receiver
device may include an HTTP server for communicating with a browser
application running on the main processor system. The browser
application presents multimedia content, received via HTTP,
corresponding to a URL entered or selected by a user.
Inventors: |
Sharifi; Kamran; (Toronto,
CA) |
Correspondence
Address: |
WOLF GREENFIELD & SACKS, P.C.
600 ATLANTIC AVENUE
BOSTON
MA
02210-2206
US
|
Assignee: |
Analog Devices, Inc.
Norwood
MA
|
Family ID: |
40535485 |
Appl. No.: |
12/137251 |
Filed: |
June 11, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60998753 |
Oct 12, 2007 |
|
|
|
Current U.S.
Class: |
725/62 ; 370/473;
455/344; 725/39 |
Current CPC
Class: |
H04L 65/4084 20130101;
H04N 21/64315 20130101; H04N 21/6581 20130101; H04N 21/235
20130101; H04N 5/44 20130101; H04N 21/434 20130101; H04N 21/41407
20130101; H04L 65/4076 20130101; H04N 21/472 20130101; H04N 21/482
20130101; H04N 21/435 20130101; H04N 21/4345 20130101 |
Class at
Publication: |
725/62 ; 725/39;
370/473; 455/344 |
International
Class: |
H04N 7/16 20060101
H04N007/16; H04N 5/445 20060101 H04N005/445 |
Claims
1. A mobile terminal comprising: a host device having a media
player adapted to receive a multimedia stream and present a
multimedia program; a receiver device, connected to the host
device, the receiver device comprising: a receiver front end having
an antenna and a receiver front end output, the receiver front end
adapted to receive a radio frequency (RF) signal via the antenna,
and output a stream of packets from the receiver front end output;
and a processing unit having a processor output, the processing
unit adapted to receive internet protocol (IP) packets derived from
packets in the stream of packets, identify IP packets corresponding
to the multimedia stream, and output the multimedia stream from the
processor output; and an interface adapted to connect the host
device and the receiver device.
2. The mobile terminal of claim 1 wherein the receiver device
further comprises an HTTP server adapted to transmit data to the
host device via the interface.
3. The mobile terminal of claim 2, wherein: the processing unit is
a protected packet processing unit; the protected packet processing
unit further comprises an IP processing unit adapted to identify IP
packets corresponding to the multimedia stream; the packets in the
stream of packets are protected packets in the stream of packets;
and the receiver device further comprises a service information and
program specific information (SI/PSI) processing unit adapted to
extract SI/PSI tables from non-protected packets in the stream of
packets.
4. The mobile terminal of claim 3, wherein the receiver device
further comprises: a demultiplexer comprising a first output and a
second output, the demultiplexer connected to the receiver front
end output to receive the stream of packets and adapted to output
protected packets from the first output and to output non-protected
packets from the second output.
5. The mobile terminal of claim 4 wherein the receiver device
further comprises: a correction unit having an IP packet output and
connected to the first output, the correction unit adapted to
perform error correction to protected packets, and output IP
packets from the IP packet output, each IP packet corresponding to
one of the protected packets.
6. The mobile terminal of claim 5 wherein the protected packet
processing unit further comprises: a decryption engine adapted to
decrypt the multimedia stream from IP packets corresponding to the
multimedia stream, based on a decryption key and to output the
multimedia stream from the processor output.
7. The mobile terminal of claim 6 wherein: the RF signal is a first
RF signal; the receiver front end further comprises a signal
strength output, the receiver front end further adapted to output
signal strength information from the signal strength output; and
the receiver device further comprises: a receiver controller
connected to the signal strength output and adapted to configure
the receiver front end to receive a second RF signal when the
signal strength information corresponds to an undesirable
state.
8. The mobile terminal of claim 7 wherein the error correction is
multiprotocol encapsulation-forward error correction (MPE-FEC).
9. The mobile terminal of claim 7 wherein the IP packets
corresponding to the multimedia stream are in real-time transport
protocol (RTP).
10. The mobile terminal of claim 7 wherein the interface is a
serial interface.
11. The mobile terminal of claim 7 wherein the receiver device
further comprises: an electronic service guide (ESG) decoder having
an ESG output adapted to output ESG data decrypted from ESG
information, the ESG information received from IP packets
corresponding to ESG files; and a service purchase and protection
(SPP) unit adapted connected to the ESG output and to extract the
decryption key from the ESG data and provide the decryption key to
the decryption engine.
12. The mobile terminal of claim 11 wherein the receiver device
further comprises: a session description protocol (SDP) unit
adapted to extract media details from IP packets corresponding to
SDP files, and output the media details from the processor
output.
13. The mobile terminal of claim 12, wherein: the IP packets
corresponding to SDP files are delivered to the SDP unit through a
file delivery over unidirectional transport (FLUTE) parser unit and
an extensible markup language (XML) parser unit in the protected
packet processing unit; and the IP packets corresponding to ESG
files are delivered to the ESG decoder through the FLUTE parser
unit and the XML parser unit.
14. A method of operating a mobile terminal, the mobile terminal
comprising a host device and a receiver device, the receiver device
initially configured to receive packets arriving in a first time
slot, the method comprising: transmitting from the host device to
the receiver device a multimedia content selection; identifying an
address corresponding to the multimedia content selection; looking
up a packet identifier in a table stored on the receiver device,
the packet identifier corresponding to the address; reconfiguring
the receiver device to a second time slot; and transmitting
multimedia content decrypted with a decryption key from the
receiver device to the host device.
15. The method of claim 14, wherein the multimedia content
selection is transmitted as a uniform resource locator (URL).
16. The method of claim 15, wherein identifying is performed by an
HTTP server running on the receiver device.
17. The method of claim 16, wherein the HTTP server identifies the
address corresponding to the URL by decoding the URL using
information stored by a service information and program specific
information (SI/PSI) processing unit and by an electronic service
guide (ESG) decoder, wherein the SI/PSI processing unit and the ESG
decoder are modules in the receiver device.
18. The method of claim 14, wherein the multimedia content
selection and multimedia content are transmitted over a serial
interface.
19. The method of claim 14, further comprising: searching at least
one of the packets received in the first time slot for the packet
identifier.
20. A method of processing a broadcast signal by a receiver device
for transmission to a host device, the method comprising: receiving
a RF broadcast signal at the receiver device; converting, in the
receiver device, the RF broadcast signal into a baseband signal
comprising protected and non-protected packets; sorting protected
and non-protected packets in the receiver device; extracting
service information and program specific information (SI/PSI)
tables from non-protected packets and storing the SI/PSI tables to
memory in the receiver device; error correcting protected packets,
in the receiver device, wherein the error correcting produces
internet protocol (IP) packets; determining, in the receiver
device, an IP packet type based on a destination address for each
IP packet; and transmitting IP packets having an audio/video (A/V)
packet type from the receiver device to the host device, over a
serial interface, for playback.
21. A wireless communications device comprising: a host processor
including a media player and a user interface that permits a user
to select a TV channel; and a receiver block connected to the host
processor, the receiver block comprising: a receiver front end
configured to receive an RF signal containing a stream of packets;
and a processing unit configured to process at least a portion of
the received stream of packets and, in response to a request from
the host processor for the user selected TV channel, to provide
packets corresponding to the selected TV channel to the host
processor for playback by the media player.
22. The wireless communications device of claim 21, wherein the
receiver block is connected to the host processor by a serial
interface.
23. The wireless communications device of claim 21, wherein the
processing unit comprises a decryption engine adapted to decrypt
the packets corresponding to the selected TV channel based on a
decryption key.
24. The wireless communications device of claim 21, wherein the
receiver block further comprises an HTTP server, wherein the
processing unit provides the packets corresponding to the selected
TV channel to the host processor in hypertext transfer protocol
(HTTP) through the HTTP server.
25. The wireless communications device of claim 24, wherein: the
processing unit is a protected packet processing unit; the
protected packet processing unit further comprises an IP processing
unit; the packets corresponding to the selected TV channel are of a
protected packet type; and the receiver block further comprises a
service information and program specific information (SI/PSI)
processing unit adapted to extract SI/PSI tables from non-protected
packets in the stream of packets.
26. The wireless communications device of claim 25, wherein the
receiver block further comprises: a correction block to perform
error correction to the protected packets and to send the protected
packets after error correction to the protected packet processing
unit; a demultiplexer adapted to send protected packets to the
correction block and non-protected packets to the SI/PSI processing
unit; and a receiver controller to monitor a signal strength of the
RF signal and reconfigure the receiver front end based on
information in the SI/PSI tables when the signal strength
corresponds to an undesirable state.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims the benefit, under 35 U.S.C.
.sctn.119(e), of U.S. Provisional Application Ser. No. 60/998,753,
filed Oct. 12, 2007, entitled "Mobile TV System Partitioning For
Mobile/Portable Terminal Devices," which application is hereby
incorporated herein by reference in its entirety.
FIELD OF INVENTION
[0002] This invention relates to mobile wireless terminals and,
more particularly, to a system architecture that facilitates
integration of mobile TV service into a mobile wireless
terminal.
BACKGROUND
[0003] For some consumers, it is desirable to "stay connected" at
all times. Current mobile phones support some form of non-voice
connectivity such as text messaging, allowing users to subscribe to
various information services. These services provide periodic
content as it becomes available or on demand from the user. Many
mobile phones now support some form of Internet browsing, email
access, downloading, and other forms of information transfer.
[0004] Standards are currently being established for digital TV
broadcasts to a variety of wireless mobile terminals, and the
availability of such services is expected to increase in the coming
years.
[0005] Mobile terminals can take the form of a mobile phone, a
personal digital assistant (PDA), a portable media platform (PMP),
or any similar product that is capable of storing, processing,
playing-back, and communicating digital content wirelessly.
[0006] FIG. 1 is a block diagram of a mobile terminal 100P capable
of receiving TV signals. Mobile terminal 100P includes a mobile TV
receiver 200P and a main processor system 300P. Many mobile
terminals include additional functions and interfaces. For example,
a mobile phone may include a mobile phone front-end receiver module
that allows connectivity to a cellular network such as a GSM, EDGE,
or 3G network, a display, a keyboard, headphones, speakers,
microphones, a power management system, a camera, an
audio/video/image codec and player, and the like.
[0007] In the main processor system 300P, the functions are divided
into four main operational blocks, including, a cellular subsystem
302, an A/V subsystem 304, a host processor and memory subsystem
306, and a human interface 308. Other interfaces such as WLAN,
Bluetooth, GPS, HDMI and the like, not shown in FIG. 1 may also be
present.
[0008] The mobile TV receiver 200P includes a tuner 202, an
analog-to-digital converter (ADC) 204, a demodulator processor and
memory 206, and an antenna 208. Radio frequency (RF) communications
are received through the antenna 208. The RF signal carries the
modulated digital broadcast signal that includes a digital TV
signal in addition to other types of broadcast data. The RF signal
band, digital modulation scheme, signal bandwidth, and error
correction method are specific to the standard utilized by the
system. Signal bands between VHF and L band are used, with some
systems using higher frequencies. The digital modulation schemes
may include QPSK, DQPSK, 16-QAM, 64-QAM and the like. The channel
bandwidth to carry TV signals is typically 1.5, 5, 6, 7, or 8 MHz,
although other bandwidths are possible. Error correction methods
such as convolutional, Reed-Solomon, and Turbo codes may be used to
correct multi-byte data packets.
[0009] The mobile TV receiver 200P handles RF signal tuning and
reception, analog-to-digital conversion, and signal demodulation,
and provides digital data to the main processor system 300P for
further processing. Cost, size, and power considerations usually
demand that a serial interface 110P be used for communication
between the receiver and the main processor system. Once the
digital data has reached the main processor system 300P, additional
processing is performed. Additional processing performed by the
main processor system 300P includes error correction, decryption,
decoding, play-back and the like.
[0010] Like conventional television, mobile TV is a broadcast
system, so data flow is primarily from the mobile TV receiver 200P
to the main processor system 300P. Control information is sent from
the main processor system 300P to the mobile TV receiver 200P to
control receiver operation.
[0011] One of the standards for mobile TV is DVB-H, or Digital
Video Broadcasting-Handheld. DVB-H is an extension of DVB (Digital
Video Broadcasting) that addresses the two main issues of
broadcasting to a mobile user: power consumption of the terminal
and the Doppler Effect--since users may be traveling at relatively
high speeds (e.g., in a car or train).
[0012] To reduce power consumption, DVB-H utilizes a slicing scheme
in which data is sent and received during pre-defined and limited
time slots. This allows the receiver to partially shut down outside
of the active time slots.
[0013] Improved reception quality is achieved by extensive error
coding and error correction schemes.
[0014] In DVB-H, broadcasts data is sent in the form of fixed size
(188 bytes) MPEG-2 (Motion Picture Experts Group) transport stream
(TS) packets. FIG. 2 shows the structure of an MPEG-2 TS packet
400P which includes a header 410, a packet identifier (PID) 420,
and a payload 430. Depending on the contents of payload 430,
packets may be protected packets 432 or non-protected packets
434.
[0015] The payload of non-protected packets 434 carries tables of
information about the services (Service Information, SI) and
programs (Program Specific Information, PSI) that are being
broadcast. SI and PSI tables are a part of the broadcast service
delivery and are required to navigate through different types of
information available in each MPEG-2 TS packet. They are used to
decode the selected audio, video, picture, and/or other digital
content.
[0016] The payload of protected packets 432 carries internet
protocol (IP) datagrams, i.e., IP packets. The IP packets contain
audio, video, image and graphics data related to each program.
Additionally, the IP packets can deliver other types of information
such as an electronic service guide (ESG), data files, news,
traffic data, financial market data, and graphical newspapers, or
any other type of multimedia content. Here and throughout, the
phrase "multimedia content" refers to any type of content that may
be broadcast to a mobile terminal. Mobile terminals supporting
Internet Group Management Protocol (IGMP) additionally may receive
content associated with groups to which the mobile terminal has
privileges.
[0017] FIG. 3 represents a conventional architecture for mobile
terminal 100P. The mobile TV receiver 200P is partitioned into a
physical layer 210 and a data link layer 220.
[0018] In the physical layer 210, the RF tuner may be tuned to a
mobile TV channel which is demodulated and converted to a digital
signal. The digital signal is initially in the form of DVB symbols
232 which are then converted to MPEG-2 TS packets 234 by DVB-T
(Digital Video Broadcasting-Terrestrial) unit 214.
[0019] In the data link layer 220, the MPEG-2 TS packets are sorted
into protected packets 236 and non-protected packets 238 by MPEG-2
TS unit 222. MPE-FEC (multiprotocol encapsulation-forward error
correction) is performed on the protected packets to improve
carrier-to-noise ratio (C/N) and Doppler performance in MPE-FEC
unit 224. The IP packets 112 are extracted and delivered to the IP
processing unit 312 in the main processor system 300P. IP
processing unit 312 identifies the IP addresses of the IP packets
and filters the packets based on their destination addresses.
[0020] Non-protected packets 238 do not receive MPE-FEC decoding
and are passed by Non-MPE-FEC unit 226 as TS packets 114 to the
SI/PSI processing unit 314 in the main processor system 300P. The
SI/PSI tables are extracted from the TS packets by SI/PSI
processing unit 314.
[0021] The IP processing unit 312 and SI/PSI processing unit 314
residing on the main processor system 300P perform computationally
intense tasks. This places a burden on the main processor
system.
SUMMARY
[0022] A system architecture for a mobile terminal is disclosed
that facilitates the integration of mobile TV service into a mobile
terminal system.
[0023] In one aspect, embodiments relate to a mobile terminal
comprising a host device, a receiver device, and an interface. The
host device has a media player adapted to receive a multimedia
stream and present a multimedia presentation. The receiver device
is connected to the host device and comprises a receiver front end
and processing unit. The receiver front end has an antenna and a
receiver front end output. The receiver front end is adapted to
receive a radio frequency (RF) signal via the antenna and output a
stream of packets from the receiver front end output. The
processing unit has a processor output. The processing unit is
adapted to receive internet protocol (IP) packets derived from
packets in the stream of packets, identify IP packets corresponding
to the multimedia stream, and output the multimedia stream from the
processor output. The interface is adapted to connect the host
device and the receiver device.
[0024] In another aspect, embodiments relate to a method of
operating a mobile terminal. The mobile terminal comprises a host
device and a receiver device. The receiver device is initially
configured to receive packets arriving in a first time slot. The
method comprises transmitting from the host device to the receiver
device a multimedia content selection, identifying an address
corresponding to the multimedia content selection, looking up a
packet identifier in a table stored on the receiver device, the
packet identifier corresponding to the address, reconfiguring the
receiver to a second time slot, and transmitting multimedia content
decrypted with a decryption key from the receiver device to the
host device.
[0025] In another aspect, embodiments relate to a method of
processing a broadcast signal by a receiver device for transmission
to a host device. The method comprises receiving a RF broadcast
signal at the receiver device, converting, in the receiver device,
the RF broadcast signal into a baseband signal comprising protected
and non-protected packets, sorting protected and non-protected
packets in the receiver device, extracting service information and
program specific information (SI/PSI) tables from non-protected
packets and storing the SI/PSI tables to memory in the receiver
device, error correcting protected packets, in the receiver device,
wherein the error correcting produces internet protocol (IP)
packets, determining, in the receiver device, an IP packet type
based on a destination address for each IP packet, and transmitting
IP packets having an audio/video (A/V) packet type from the
receiver device to the host device, over a serial interface, for
playback.
[0026] In yet another aspect, embodiments relate to a wireless
communications device. The wireless communication device comprises
a host processor and a receiver block. The host processor includes
a media player and a user interface that permits a user to select a
TV channel. The receiver block is connected to the host processor
and comprises a receiver front end and a processing unit. The
receiver front end is configured to receive an RF signal containing
a stream of packets. The processing unit is configured to process
at least a portion of the received stream of packets and, in
response to a request from the host processor for the user selected
TV channel, to provide packets corresponding to the selected TV
channel to the host processor for playback by the media player.
BRIEF DESCRIPTION OF DRAWINGS
[0027] The invention and embodiments thereof will be better
understood when the following detailed description is read in
conjunction with the accompanying drawing figures. In the figures,
elements are not necessarily drawn to scale. In general, like
elements appearing in multiple figures are identified by a like
reference designation. In the drawings:
[0028] FIG. 1 is a block diagram of a mobile terminal;
[0029] FIG. 2 is a block diagram of the structure of an MPEG-2 TS
packet;
[0030] FIG. 3 is a block diagram of a conventional architecture of
a mobile terminal;
[0031] FIG. 4 is a block diagram of the mobile terminal
architecture according to some embodiments; and
[0032] FIG. 5 is a flowchart for selecting and connecting to a
mobile TV station according to some embodiments.
DETAILED DESCRIPTION
[0033] Mobile terminals are very complex devices that offer a wide
variety of functions. Different terminals offer different features,
hardware/software capabilities, user interfaces, connection
technologies, and available applications for the end user. Because
of the diversity, variety, and complexity of mobile terminals,
integrating TV and/or other broadcast services into these terminals
may be a complicated task.
[0034] A system architecture is disclosed that facilitates the
integration of the mobile TV service into a mobile terminal system
by providing standard-based, well-understood, widely used and
ubiquitous networking and programming interfaces. Introduction of
such an interface will enable the mobile TV service to be added to
the main processor software as a plug-in module, thus reducing the
complexity of software integration tasks. The disclosed
architecture also reduces the MIPS (Million Instructions Per
Second) loading, memory, and timing requirements for the mobile
terminal's main processor system. This can lead to an increase in
efficiency and throughput of the interface between the mobile TV
receiver module and the mobile terminal main processor system.
[0035] For convenience, Table 1 lists some of the terms used in
this specification.
TABLE-US-00001 TABLE 1 Table of Terms Acronym Meaning A/V
Audio/Video ADC Analog-to-Digital Converter AES Advanced Encryption
Standard API Application Programming Interface ARQ Automatic
Repeat-Request C/N Carrier-to-Noise Ratio DVB Digital Video
Broadcasting DVB-H Digital Video Broadcasting-Handheld DVB-T
Digital Video Broadcasting-Terrestrial ESG Electronic Service Guide
FEC Forward Error Correction FLUTE Filed Delivery over
Unidirectional Transport GUI Graphical User Interface HTML
HyperText Markup Language IGMP Internet Group Management Protocol
IP Internet Protocol LCD Liquid Crystal Display MFN Multi-Frequency
Networks MIPS Million Instructions Per Second MPE-FEC Multiprotocol
Encapsulation-Forward Error Correction MPEG Motion Picture Experts
Group PID Packet Identifier PSI Program Specific Information RF
Radio Frequency RTP Real-Time Transport Protocol SDP Session
Description Protocol SI Service Information SPP Service Purchase
and Protection TS Transport Stream UDP User Datagram Protocol URL
Uniform Resource Locator VDP Variable Data Printing XML Extensible
Markup Language
DESCRIPTION OF AN EMBODIMENT OF MOBILE TERMINAL 100
[0036] FIG. 4 is a block diagram of a mobile terminal 100 according
to some embodiments of the invention. The mobile terminal 100 is
functionally partitioned into a Host/Application main processor
system 300 and a mobile TV receiver device 500.
[0037] Communication between the mobile TV receiver device 500 and
the main processor system 300 may be performed over an interface
110. While interface 110 is typically a serial interface, any other
type of interface for communicating data between the main processor
system 300 and the mobile TV receiver device 500 may be used, such
as a parallel interface.
[0038] In some embodiments, main processor system 300 is
implemented as one or more integrated circuits, such as a digital
signal processor, and mobile TV receiver device 500 is implemented
as a separate integrated circuit and/or other hardware. In some
embodiments, mobile TV receiver device 500 and main processor
system 300 may be combined onto the same integrated circuit.
Main Processor System 300
[0039] Main processor system 300 is adapted to execute an A/V CODEC
and media player 360, a user interface 330, a mobile TV application
340, a service guide 350, a browser application 370, and may have
other components not shown. The A/V codec and media player 360 may
decode the media stream (that is to decompress the compressed media
stream) and play back the video and audio contents. For example,
the video and audio contents may be played back over an LCD display
and a speaker system, respectively. The user interface 330 may
receive input signals from the user and transmit the control
signals from such input devices as keyboard, touch sensor screen,
buttons, stylus or similar devices to the main processor. The
mobile TV application 340 may be a software that allows the user to
select a specific TV channel for viewing. It may also verify that
the user has the right privileges for viewing a particular channel.
The service guide 350 may collect all the information about
available channels and their schedule in a tabular form. The
browser application 370 may provide the familiar browser graphical
user interface on a display screen. It also provides the graphical
environment to display the video component of the TV, or the
service guide. In some embodiments, the main processor system 300
may be made of identical or similar hardware as the main processor
system 300P (FIG. 1) of the prior art.
[0040] The main processor system 300 may present the multimedia
content through a stand-alone program or through a browser
application similar to Microsoft Internet Explorer, Mozilla
Firefox, or any other embedded browser application software. The
browser application may provide a familiar look and feel to
users.
Receiver Device 500
[0041] The receiver device 500 digitizes received RF communications
and performs network layer and additional processing prior to
sending multimedia content to the main processor system 300. The
receiver device 500 may contain a receiver front end 510, a
demultiplexer 520, an error correction unit 530, a protected packet
processing unit 550 containing an IP processing unit 540, a
non-protected packet processing unit 560, an HTTP server 570, and a
receiver controller 580. Each of these units is described
below.
Receiver Front End 510
[0042] The receiver front end 510 provides the functionality of a
receiver unit with a digital signal output. The receiver front end
510 may be adapted to receive signals of any RF band appropriate
for transmission of multimedia content. In some embodiments, tuner
512 selects the desired signal band, and suppresses unwanted
signals. RF communications may be received by an antenna 518.
[0043] The RF signal received by receiver front end 510 may be
digitized and demodulated. Digitization and demodulation may be
performed using hardware, software, or any other suitable means. In
some embodiments the RF signal is converted to a digital signal by
an analog-to-digital converter (ADC) 514, and may then be
demodulated by demodulator 516.
[0044] The receiver front end 510 outputs a digital signal
containing received information to demultiplexer 520. In
embodiments supporting DVB-H broadcasts, the signal output to
demultiplexer 520 may be in the form of MPEG-2 TS packets. In some
embodiments, a signal strength output measurement is provided to
receiver controller 580.
Demultiplexer 520
[0045] Demultiplexer 520 distributes portions of the digital signal
received from receiver front end 510 to various receiver
components, such as protected packet processing unit 550 and
non-protected packet processing unit 560.
[0046] In some embodiments, the digital signal is received as a
series of packets. The demultiplexer 520 sorts the packets based on
packet type. In embodiments for receiving DVB-H broadcasts, packets
may be sorted into protected packets and non-protected packets.
Error Correction Unit 530
[0047] Packets requiring error correction (e.g., protected packets,
MPEG-2 TS protected packets, MPE-FEC packets) are sent to the error
correction unit 530 by the demultiplexer 520. Error correction unit
530 may perform any suitable error correction method. In
embodiments where the receiver device does not send signals back to
the transmission station, automatic repeat-request (ARQ) is not
practical, and forward error correction (FEC) may be used. In
embodiments for receiving a DVB-H broadcast, multiprotocol
encapsulation-forward error correction (MPE-FEC) may be performed
on protected packets.
[0048] Error corrected packets are output from the error correction
unit 530 to the protected packet processing unit 550. In
embodiments for receiving a DVB-H broadcasts, error correction unit
530 outputs user datagram protocol (UDP) formatted IP packets to
the protected packet processing unit 550.
Protected Packet Processing Unit 550
[0049] The protected packet processing unit 550 extracts the
payload of each packet received from the error correction unit 530
(e.g., protected packets 432, FIG. 2). In some embodiments, the
error corrected IP packets are output from the error correction
unit 530 in the UDP format to the IP unit 551 of the protected
packet processing unit 550. The IP packet payload and delivery
information may be extracted by IP unit 551.
[0050] In some embodiments supporting IGMP, IP unit 551
additionally receives information from IGMP unit 553 for
identifying packets pertaining to broadcast data directed to a
messaging group with which mobile terminal 100 is associated.
[0051] The payloads extracted by IP unit 551 are directed to the IP
processing unit 540. The content of each payload is determined by
the IP processing unit 540. Payloads may include multimedia content
(e.g., A/V packets), information needed for decryption (e.g.,
electronic service guide files), media session information (e.g.,
session description protocol files), and any other information
necessary for presenting multimedia content. IP processing unit 540
identifies and directs payloads to the file delivery over
unidirectional transport (FLUTE) module 544 or the real-time
transport protocol (RTP) module 542 based on their packet type as
determined by a destination address and UDP port number.
[0052] Packet types relevant to DVB-H broadcasts include electronic
service guide (ESG) files, session description protocol (SDP)
files, and A/V packets. ESG files carry information on how the
broadcast A/V data is encrypted. Packets that contain ESG files are
delivered to an ESG decoder 552 through FLUTE module 544 and an XML
(extensible markup language) parser 546 for extraction of relevant
information.
[0053] The FLUTE protocol helps in obtaining an error-free delivery
of a file over a unidirectional broadcast channel. FLUTE module 544
may be part of IP processing unit 540 and is used primarily in
dealing with FLUTE protocol packets containing ESG files and SDP
files.
[0054] The ESG decoder 552 decrypts the ESG information using
standards-based decryption algorithms such as 128-bit AES (advanced
encryption standard). The operation that controls the decryption
process and manages the decryption keys relies on the extracted
information from the ESG files and is called a service purchase and
protection (SPP) helper process unit 554. The SPP helper process
unit 554 may extract the updated decryption keys from the ESG data
and provide the decryption keys to the decryption engine 548. The
decryption engine uses the decryption keys to decrypt the A/V data
before sending it to the main processor system 300.
[0055] Session description protocol (SDP) module 556 provides a
standard representation of the information required to initiate a
streaming media session, such as viewing a broadcast digital TV
channel. The standard representation may include information such
as bit rate, type of audio/video compression, transport addresses,
and other types of media details. Packets that contain SDP files
are recognized by their IP destination address and UDP port number
and are delivered to the host media player 360 through FLUTE module
544 and XML parser 546. When the SDP file is extracted from FLUTE
data, it can be presented to the A/V CODEC and media player 360 of
the main processor system 300.
[0056] A/V packets contain actual compressed audio/video tracks for
the requested channel or program and are sent from the IP
processing unit 540 via the RTP unit 542 to the media player 360
running on the main processor system 300 via RTP protocols. In some
embodiments where decryption is used, the A/V packets are decrypted
by the decryption engine 548 which receives the necessary
decryption keys from SPP helper process unit 554.
HTTP Server 570
[0057] In some embodiments, the multimedia content and session
information are sent to the main processor system 300 using HTTP
server 570. The HTTP server 570 transmits multimedia content to the
main processor system 300 using hypertext transfer protocol (HTTP).
The multimedia content may be displayed through a browser
application 370 running on the main processor system 300.
[0058] The HTTP server 570 may also receive information from the
main processor system 300. For example, in some embodiments a user
may select a TV channel for viewing through a web browser
application. The request may be sent to the HTTP server 570 of
device 500 via HTTP, in the form of a uniform resource locator
(URL), over the serial interface 110. In such configuration, the
list of available programs is presented graphically in the window
of the browser application 370, and a scroll bar in the browser may
allow the user to scroll onto the TV channel to be watched. In some
embodiments, simply clicking on the bar (or tapping the screen if a
touch sensor is used) will enable the viewing of the TV channel of
interest.
Non-Protected Processing Unit 560
[0059] Packets not requiring error correction (e.g., non-protected
packets) by error correction unit 530 are directed to the
non-protected processing unit 560 by the demultiplexer 520. The
non-protected processing unit 560 may extract and store tables
containing information needed to decode the multimedia content.
Also extracted in some embodiments is network map information,
which provides details on the signal coverage for the surrounding
geographic space. In embodiments supporting DVB-H broadcasts, the
non-protected processing unit 560 receives the non-protected
packets from the demultiplexer 520. The extracted tables are SI/PSI
(Service Information/Program Specific Information) tables which are
stored in embedded memory 564.
[0060] The non-protected packet processing unit 560 includes the
SI/PSI processing unit 562 and memory 564. The SI/PSI processing
unit 562 navigates through the received TS packets, extracts the
relevant SI/PSI tables and stores them in memory 564. The SI/PSI
tables may contain information about the available frequency bands,
networks, channels, and programs. The tables also include the IP
addresses of those IP packets containing compressed audio/video
data for broadcast programs and packets containing ESG.
Receiver Controller 580
[0061] The receiver controller 580 may control the receiver front
end 510. At start up, the receiver controller may configure the
receiver front end and instruct it to scan for available content
bands. Signal strength measurements provided from the receiver
front end 510 may be used to determine if the receiver should be
reconfigured to receive content from a different transmitter.
[0062] In embodiments where handover from one transmitter to
another requires a change in tuner configuration, the receiver
controller 580 enables the seamless reconfiguration of the receiver
front end without perceptible interruption of content.
[0063] Receiver controller 580 may include a frequency scan unit
582 and a handover unit 584. In Multi-Frequency Networks (MFNs), a
handover takes place when a mobile terminal 100 leaves a coverage
area of a first cell and enters a coverage area of a second cell.
In MFNs, transmitters of neighboring cells operate at different
frequencies. In some embodiments, handover is managed by the mobile
TV receiver device 500 without involvement of the main processor
system 300. In DVB-H systems, handover may involve a change in
frequency and/or change in the transport stream that carries the
desired signal. The time slicing feature of DVB-H allows for the
seamless handover from the first cell to the second without
interruption of service.
[0064] Radio signal strength may be monitored by receiver
controller 580. The SI/PSI tables stored in memory 564 contain
network map information and how the area is covered by multiple
antennas. This information is provided to handover unit 584. When
the signal strength of the tuned frequency band decreases below a
threshold, the handover unit may cause the tuner 512, via frequency
scan unit 582, to tune to a different frequency band based on the
network map data.
[0065] In some embodiments, the broadcasts from adjacent cells may
be monitored during the off-time in DVB-H systems. The signal
strength for the neighboring cells is measured. The handover unit
584 may cause the frequency scan unit 582 to tune to the cell of
the same network with the strongest signal. By synchronizing to the
new frequency, the transport stream of the same IP stream is found
in the new cell and the relevant content is sent to the main
processor system 300 without interruption of service.
[0066] The frequency scan unit 582 may control tuner 512. If no
frequency band is preset, frequency scan unit 582 starts a scanning
process by configuring tuner 512 for the proper mode and registers
all the available bands. This list is stored in memory 564 and is
available to the main processor system 300 upon invocation of an
appropriate API (application programming interface) such as mobile
TV application 340. In some embodiments, a GUI (graphical user
interface) may present this list to the user. A graphical
presentation may also be made by the browser application 370.
Method of Operating a Mobile Terminal 100
[0067] In some embodiments, a user may select a channel for viewing
from a list of channels provided by user interface 330. An
embodiment of a selection process is shown in FIG. 5. The list of
channels may be stored in the main processor system 300 and is
derived from the ESG and SI/PSI data processed by the mobile TV
receiver device 500. In embodiments where the main processor system
300 is running a browser application, the user directly or
indirectly selects the URL of the desired channel (step 602). The
URL, which may reference the TV station or channel, e.g.
www.bbc.co.uk/mobiletv, is sent from the browser application on the
main processor system 300 over the serial interface to the HTTP
server 570 running on the mobile TV receiver device 500 (step
604).
[0068] The received URL is decoded into an IP address by the HTTP
server 570. HTTP server 570 relies on the information stored in the
SI/PSI tables by non-protected packet processing unit 560 on the
mobile TV receiver device 500 as well as the information decoded
and stored by the ESG decoder 552 (step 606).
[0069] At step 608, the IP address is accessed from a table in
memory 564 that is regularly updated by the SI/PSI processing unit
562 and the ESG decoder 552.
[0070] The result of the access is reported in step 610. The result
may be a list of packet identifiers (PID's) for the TS packets that
contain the desired A/V stream. The list of PIDs for a channel is
extracted for the non-protected packets by the SI/PSI processing
unit 560.
[0071] Once the PIDs for a specific TV channel are known, a search
is conducted to determine if the TS packets with that PID are
already being received and if they are being corrected into IP
datagram, and if they are further processed by the RTP module 542,
and sent to the main processor system 300 (step 612) for decode and
play back. If so, the channel is displayed using the user
interface.
[0072] If the desired PID is not being received, the mobile TV
receiver device 500 switches to the time slot where the PID is
being sent (step 614). The appropriate time slot information is
extracted by the SI/PSI processing unit 562.
[0073] The RF signal band, digital modulation scheme, signal
bandwidth, and error correction method are specific to the standard
utilized by the system.
[0074] It should be appreciated that components of a mobile
terminal may be implemented as hardware, software, or a combination
of both. Having thus described at least one illustrative embodiment
of the invention, various alterations, modifications, and
improvements will readily occur to those skilled in the art. Such
alterations, modifications, and improvements are intended to be
within the scope of the invention. Accordingly, the foregoing
description is by way of example only and is not intended as
limiting. The invention is limited only as defined in the following
claims and the equivalents thereto.
* * * * *
References